In recent years, as one of measures against environmental issues, attention is focusing on a hybrid vehicle, a fuel cell vehicle, an electric vehicle, and the like that run with a driving force from a motor. Such a vehicle may have mounted thereon a power storage device for supplying electric power to the motor and a charging device for charging the power storage device through use of an external power supply.
When charging the power storage device, it is necessary to prevent overcharging so as to avoid degradation of the power storage device from being expedited. In view of such a problem, Japanese Patent Laying-Open No. 05-316663 (PTL 1), for example, discloses a method of charging a storage battery to prevent overcharging when charging a storage battery having been less discharged. This method of charging a storage battery is a method of charging a storage battery in which high rate battery charge is performed until the terminal voltage of the storage battery attains a gas generating voltage, and then trickle charge is performed for a timer time, wherein control is exercised such that a variable per unit time of the terminal voltage of the storage battery is detected during trickle charge, and when this variable is smaller than a full-charge determination value, the timer time is changed to be shorter in accordance with a lapsed time of trickle charge and count-up is continued, and in contrast, when the variable is larger than the full-charge determination value, count-up is continued as it is by the end of the timer time.
The method of charging a storage battery disclosed in the publication mentioned above prevents overcharging when charging a storage battery having been less discharged, which can prevent degradation of the storage battery.